EP0184106B1 - Resin solutions for putty and coating compositions, process for their preparation and their use - Google Patents

Abstract

Resin solution for cements and coating compositions based on a reaction product of epoxy resins having more than one epoxy group in the molecule and furfuryl alcohol alone or in admixture with other furan derivatives dissolved in reactive diluents and process for its preparation. These resin solutions are used for preparing cements and coating compositions by mixing the resin solution immediately before use with (A) at least one filler and (B) at least one curing agent or a mixture of (A) and (B), the weight ratio of the solution to the sum of components (A) and (B) being 1:(0.5-7), preferably 1:(1-4).

Description

It is known to use polycondensates of furfuryl alcohol as binders for acid-curing putties. The second main component of these putties are fillers, to which acids or acid-releasing substances are added as hardening catalysts, which cause hardening without the addition of heat.

It is also known from DE-C 2,926,053 to react furfuryl alcohol with a hydroxymethyl group-containing alkylphenol resol based on bifunctional alkylphenols at elevated temperature and to react the reaction product in at least one reactive diluent from the group consisting of benzyl alcohol, low molecular weight epoxy compounds, furfurol and difuryl ether, Dissolve furfuryl alcohol in order to avoid the otherwise severe post-shrinkage of furan kittens. The addition of low molecular weight epoxy compounds does not affect the elastic behavior of the hardening products, but they have a certain sensitivity to some aggressive, organic solvents, which are of importance in practice for a number of cases, such as ketones, chlorinated and aromatic hydrocarbons, and esters.

The presence of furfuryl alcohol in plastic cements consisting of 1.5-1.6% by weight furfuryl alcohol, 14-16% by weight furan-epoxy binder, 2.8-3.2% by weight polyethylene polyamine and mineral fillers is said to another publication (SU-PS 619 464), on the one hand increase the strength of these cements and on the other hand reduce the post-shrinkage. Such a material is used in the construction industry to produce corrosion-resistant coatings and as a chemically resistant material for floor coating. However, the shrinkage is relatively high at 0.75%.

These crosslinking products are also unsuitable for the production of putty resins or putties that are exposed to high chemical stresses because, because of their amine content, they inhibit the acid catalysis required to cure the putty and, in addition, do not have sufficient acid and alkali resistance in the crosslinked state.

DE-B-1 113 565 discloses the reaction of epoxy resins with furfuryl alcohol in the presence of Friedel-Crafts compounds, metal fluoroborates or boron trifluoride as catalysts. However, only cured plastics such as castings but no storage-stable resin solutions are obtained by this process.

In the patent US-A-4,100,314 it is described to use a synthetic resin solution as a coating agent for tar-impregnated carbon bodies, which consists of crosslinking furan compounds e.g. a mixture of equal parts of furfurol and furfuryl alcohol, diethyl sulfate as a catalyst and epoxy resins. Crosslinking takes place at temperatures between 100 and 135 ° C and is therefore not suitable for the production of kittens alone, because they have to crosslink at room temperature or at least close to room temperature.

It is also known to modify furan resins in a variety of ways. So you can convert furfurol with phenol to novolaks, which are used for the production of phenolic resin molding compounds. However, because of their inherently high viscosity, these resins cannot be used for the production of kittens.

It is also known to modify furfuryl alcohol condensates with urea and formaldehyde and to use these polycondensates as core binders. But even the known inclusion of phenol in this modification does not change the poor chemical resistance and low thermal resistance of these polycondensates, which is generally necessary in the production of core binders.

The known reaction of furfuryl alcohol with phenols or with resorcinol does not lead to suitable resins for putties or coating compositions, but rather to resins which can only be used as binders for glues, molding compounds or lacquers. Likewise, the reaction between hydroxybenzyl alcohol and furfuryl alcohol does not provide a suitable putty resin. When trying to mix such polycondensates with a filler containing acidic catalysts, a stormy polycondensation reaction takes place. The hardening product thus obtained shrinks and is also very susceptible to alkali.

DE-A-27 50 704 describes the preparation of reaction products from hydroxyaromatic compounds, formaldehyde and furfuryl alcohol, where the furfuryl alcohol can optionally also be used in such an excess that it acts as a solvent. In addition, the reaction product can be cured with acidic catalysts. According to this publication, these known resol resins modified with furfuryl alcohol are to be processed with other monomers, such as isocyanates, into flame-retardant compact moldings, but preferably into foams. The production of kittens was not considered.

The furan resins usually used in the manufacture of acid-curing putties result in putties very good chemical resistance. In particular the furan putties are highly alkali-resistant. Disadvantages of furan putties, however, are their relatively high brittleness, which precludes their use in special applications, for example when cementing apparatus parts, but especially when used in coating compositions which are meant in the narrower sense. The modulus of elasticity of the hardened putty is 1.2 to 2.0 N⁶. cm². This relatively high modulus of elasticity of the furan resin putty previously used is disadvantageous because of the brittleness involved. The brittleness can lead to the risk of detachment from the substrate and cracks in tile coverings made of acid-resistant ceramic materials laid with furan resin putty if the different thermal expansion coefficients of putty, ceramic materials and the substrate become effective due to temperature changes or changes in temperature. The bond between putty, ceramic material and substrate is less sensitive to cracking and detachment when the temperature changes, the lower the modulus of elasticity of the putty. The putty is then less brittle and greater deformability is possible without crack formation and detachment. The temperature resistance of the furan resin putties previously used was generally around 200 to 210 ° C. The same laws apply to coating compounds. Because of the disadvantages mentioned, the use of these furan resins for putties or coating compositions has not been described hitherto. It is therefore desirable to have putties and coating compositions available which do not have the disadvantages described.

Resin solutions are known from US Pat. No. 3,491,041, which contain reaction products of epoxy resins and furfuryl alcohol dissolved in excess furfural alcohol and new solvents.

The invention now relates to resin solutions for putties and coating compositions and to a process for their preparation in which epoxy resins are dissolved in furfuryl alcohol alone or in a mixture with other furan derivatives and in Temperatures between 20 and 200 ° C preferably between 40 and 140 ° C in the presence of catalysts are implemented in such a way that the reaction takes place with complete conversion of the epoxy groups with furfuryl alcohol or furan derivatives, the catalyst being neutralized after the reaction if necessary and the Reactive mixture is only mixed with reactive diluents.

Surprisingly, the putties produced according to the invention show, in addition to a long shelf life, all the positive properties of furan resin putties, excellent chemical resistance and thermal resistance up to temperatures of 320 ° C. In addition, the putties are very low in shrinkage. In addition, they have a shortened hardening time with a good service life and are nevertheless extremely resistant to chemicals.

All epoxy resins which contain more than one epoxy group per molecule can be used as epoxy resins, e.g. those obtained by reacting epihalohydrins with polyhydric alcohols or polyglycol ethers or by epoxidation of double bonds, e.g. by epoxidation of unsaturated fatty oils or unsaturated hydrocarbons, e.g. Dicyclopentadiene, butadiene, etc. can be produced. Epoxy resins obtained from diphenylalkanes or higher polyphenylolanes such as novolaks and epihalohydrins or dihalohydrins, preferably epichlorohydrin, are preferred. They generally have an epoxy equivalent weight of 150 to 2000, preferably 170 and 1200.

The epoxy resins are reacted with furfuryl alcohol or in a mixture with other furan derivatives by dissolving the epoxy resins, for example, in furfuryl alcohol and reacting them at temperatures between 20 ° C. and 200 ° C., preferably between 40 ° C. and 140 ° C. in the presence of catalysts until the epoxy groups are implemented. The complete implementation can be checked by determining the epoxy content of the reaction mixture or by determining the dry residue.

While when acidic catalysts are used they have to be neutralized after the reaction, such neutralization is not always necessary when using basic catalysts.

Strong mineral acids, alkyl or aryl sulfonic acids can be used as catalysts for the reaction of the epoxy resins with furfuryl alcohol. However, it is preferred to work with basic catalysts. Suitable catalysts are especially the hydroxides of the alkali metals, e.g. also in the form of their aqueous solutions. It is also possible to use tertiary alkylamines with 1-6, preferably up to 4, carbon atoms in the alkyl radical, such as trimethylamine, triethylamine, tert-butylamine, etc., as catalysts. Trialkyls which additionally have primary or secondary amino functions, e.g. Dimethylaminopropylamine. When using these amines, which are introduced into the epoxy resin via their primary and / or secondary amine groups, it must be ensured that their amount is only so small that it does not impair the subsequent acid curing. If the amine catalysts are used in large amounts, their removal from the reaction mixture is generally always appropriate, and it can also be done by salt formation.

It is also possible to use furan derivatives such as furfurol, hydroxymethylfurfurol, difuryl ether and others in addition to furfuryl alcohol. These compounds can be present during the reaction or can be mixed in subsequently, the excess acting as a reactive diluent.

• A. mindestens einem Füllstoff und
• B. mindestens einem Härter

vermischt wird, wobei das Gewichtsverhältnis der Harzlösung zu der Summe der Komponenten A und B 1:(0,5 bis 7) vorzugsweise 1:(1 bis 4) beträgt. Die eingesetzten Harzlösungen haben im allgemeinen einen Festharzanteil von 10 bis 75 vorzugsweise 25 bis 70, insbesondere 45 bis 55 Gew.-% Festkörpergehalt.The invention also relates to the use of the resin solutions prepared according to the invention for putties and coating compositions, in which the resin solution is used immediately before use

• A. at least one filler and
• B. at least one hardener

is mixed, the weight ratio of the resin solution to the sum of components A and B being 1: (0.5 to 7), preferably 1: (1 to 4). The resin solutions used generally have a solids content of 10 to 75, preferably 25 to 70, in particular 45 to 55% by weight solids content.

According to the claimed use, the modified furan resins are used exclusively in reactive diluents, the weight ratio of diluent to solid resin generally being (0.4 to 1.5): 1, preferably (0.6 to 1.1): 1. Diluents are e.g. Benzyl alcohol, low molecular weight epoxy compounds such as diglycidyl ether, diphenylol propane diglycidyl ether, but above all furfural, difuryl ether, preferably furfuryl alcohol. However, this and the furan components can already be present in excess from the outset during the reaction with the epoxy compounds. The storage life of the resin solutions is practically unlimited. They generally have viscosities between 50 and 20,000, preferably 100 and 15,000 mPa.s / 20 ° C.

As filler A) in the preparation of the putties, rock flour such as clay and chamotte, barium sulfate, quartz powder and preferably coke powder or graphite powder, e.g. Artificial graphite.

Acid and / or acid-forming substances, for example (a) inorganic or organic acids, such as sulfuric acid, hydrochloric acid, phosphoric acid, can be used as hardener B) for hardening the putties. usually in aqueous solution, oxalic acid, sulfonic acids, such as amidosulfonic acid, mono- and disulfonic acids of benzene, toluene, xylene, also naphthalenedisulfonic acids and / or (b) acid-releasing substances such as sulfochlorides of the sulfonic acids mentioned under (a), for example toluene or benzene sulfochloride , Alkyl esters of these sulfonic acids or acidic sulfuric acid esters and / or (c) acidic salts of sulfuric acid or phosphoric acid, preferably their sodium salts. Adducts of urea and aromatic sulfonic acids are also used individually or in a mixture with the above resins. The proportion of the hardener is 4 to 12, preferably 6 to 8% by weight of the filler-hardener mixture.

The putties are prepared by mixing the solution of the furan resin with a filler A) and catalyst or hardener B) immediately before use. In general, a mixture of filler and hardener substance, the so-called putty powder, is prefabricated and added to the furan resin solution. The putty obtained is then placed on or between the materials to be cemented using the usual methods. To evaluate the putty, the properties of the furan resin, the properties of the putty after mixing the furan resin with the putty powder, the course of curing and the chemical and physical properties of the end product are used. The furan resin should have a low degree of condensation and thus a low viscosity so that it flows and wets the filler well. If necessary, the proportion of reactive thinner should be set so that processing is possible. Good storage stability is another prerequisite for optimal use. The degree of condensation should only increase insignificantly during storage, because an excessive increase in viscosity would lead to poorer wetting of the filler and thus to processing errors.

The putty is made immediately before use. After mixing the filler with the furan resin, the action of the catalyst immediately increases the size of the furan resin molecule. The service life, i.e. the period between mixing and loss of processing consistency should generally be 30 minutes to 2 hours for convenient processing. After processing, it is desirable that the putty is hardened at room temperature as soon as possible and that it becomes resistant to chemicals and solvents.

In the examples below, T = parts by weight and% = percent by weight.

Examples 1 a) Preparation of the resin

1425 T of an epoxy resin based on diphenylolpropane and epichlorohydrin with an average epoxy equivalent weight of 425 were dissolved in 2013 T of furfuryl alcohol in a reaction vessel equipped with a stirrer and thermometer and brought to a temperature of 60 ° C. After adding 25.5 parts of 33% strength aqueous sodium hydroxide solution, the mixture was heated to 100 ° C. and stirred at this temperature for 4 hours.

The resin solution had a residue (1 h / 170 ° C) of 49.3%, viscosity 1250 mPa.s / 20 ° C. The alkali catalyst contained therein was neutralized with 19.1 T 80% lactic acid, a solution having a viscosity of 1200 mPa.s / 20 ° C. being obtained.

Application test

1 b) Preparation of the putty: For this test, 93 parts of carbon and 6 parts of a β-naphthalenesulfonic acid / urea adduct were used and a part of p-toluenesulfonic acid, a putty powder (100 T) and mixed with 60 parts of the resin solution (1 a). The putty produced from it had a service life of 75 minutes at 20 ° C and reached a value for the Shore hardness D of 45 after 24 hours.

Chemical testing

1 c) For the determination of the chemical resistance, cylindrical bodies with a height and a diameter of 25 mm were produced from the putty and stored at 20 ° C for 8 days. After this time, the test specimens were resistant to boiling 70% sulfuric acid, boiling concentrated hydrochloric acid and concentrated and dilute sodium hydroxide solution.

Physical exams

1 d) The linear shrinkage was measured on cylindrical test specimens with a diameter of 25 mm and a length of 90 mm, at the ends of which measuring markings made of glass were attached. The total length excluding the measurement marks was 100 mm. The test was carried out in accordance with the method according to ASTM C 358. The first length measurement was carried out 24 hours after the test specimens were produced and served as the starting value. The shrinkage at room temperature was 0.18% within an observation period of 94 days.

Determination of the flexural modulus of elasticity (see table). 2 a) Preparation of the resin

According to Example 1, 1425 parts of an epoxy resin based on diphenylolproprane and epichlorohydrin with an average epoxy equivalent weight of 950 were dissolved in 1714 parts of furfuryl alcohol and 25.5 parts of 33% aqueous sodium hydroxide solution were added at 60 ° C. and then brought to 100 ° C. After stirring for four hours Temperature, the resin had a residue of 49.5% (1 H / 170 ° C) and a viscosity of 13500 mPa.s.

After neutralization with 19.1 T 80% lactic acid, the viscosity dropped to 12500 mPa.s.

Application test

2 b) Production of the putty

For the test, a putty powder (100 parts) was prepared from 93 parts of carbon and 6 parts of ß-naphthalenesulfonic acid-urea adduct and one part of p-toluenesulfonic acid and mixed with 75 parts of the resin solution 2a) as in Example 1. The putty made from it had a service life of 80 minutes at 20 ° C and had a Shore hardness D value of 60 after 24 hours.

Chemical testing

2 c) For the determination of the chemical resistance, cylindrical bodies with a height and a diameter of 25 mm were produced from the putty and stored at 20 ° C for 8 days. After this time, the test specimens were resistant to boiling 70% sulfuric acid, boiling concentrated hydrochloric acid and concentrated and dilute sodium hydroxide solution.

Physical exams

2 d) The linear shrinkage was measured as in Example 1 d). The shrinkage at 20 ° C was 0.2% within an observation period of 94 days.

Determination of the flexural modulus of elasticity on test specimens 10 x 15 x 120 mm:

Claims (12)

1. A process for producing resin solutions for cements and coating compositions, characterized in that epoxy resins having more than one epoxy group in the molecule are dissolved in furfuryl alcohol alone or in mixture with other furan derivatives, and are reacted at temperatures of 20 to 200 °C in the presence of acidic or basic catalysts such that complete reaction of the epoxide groups with furfuryl alcohol or furan derivatives is achieved, and in that, if appropriate, the catalyst is neutralized after the reaction, and the reaction mixture is mixed with reactive diluents exclusively.
2. The process as claimed in claim 1, characterized in that the reaction temperature is 40 to 140 °C.
3. The process as claimed in claim 1 or 2, characterized in that the weight ratio of reactive diluents to solid resin is in the range of (0.4 to 1.5):1, preferably of (0.6 to 1.1):1.
4. The process as claimed in one or several of claims 1 to 3, characterized in that the resin solutions have viscosities of between 50 and 20000, preferably of between 100 and 15000, mPa·s at 200 °C.
5. The process as claimed in one or several of claims 1 to 4, characterized in that epoxy resins having an epoxy equivalent weight of 150 to 2000, preferably of 170 to 1200 are employed.
6. The process as claimed in one or several of claims 1 to 5, characterized in that furfurol, hydroxymethylfurfurol or difurylether are used as furan derivatives.
7. Use of the resin solution as claimed in one or several of claims 1 to 6 for preparing cements and coating compositions, characterized in that, immediately prior to its use, the resin solution is mixed with
   A) at least one filler and B) at least one curing agent or a mixture of A) and B), the weight ratio of the solution to the sum of components A) and B) being 1:(0.5 to 7), preferably 1:(1 to 4).
8. The use as claimed in claim 7, characterized in that rock flour, barium sulfate, quartz flour, coke flour or graphite flour are employed as component A).
9. The use as claimed in claims 7 or 8, characterized in that acidic and/or acid-forming substances are used as component B).
10. The use as claimed in one or several of claims 7 to 9, characterized in that a mixture of components A) and B), which has been prepared in advance, is used.
11. The use as claimed in one or several of claims 7 to 10, characterized in that the resin solution has a content of solid resin of 10 to 75 % by weight, preferably of 25 to 70 % by weight, and in particular of 45 to 55 % by weight.